1. Field of the Invention
The present invention relates to a webbing locking mechanism for use in a seatbelt system for protecting an occupant in an emergency of a vehicle.
2. Description of the Prior Art
In general, a seatbelt system is constructed such that, while the webbing is fastened to the occupants, there is tension in the webbing from the seatbelt wind-up device. After the unfastening of the webbing, most of the webbing is wound up and retracted.
The wind-up biasing force by the wind-up device exerts an uncomfortable oppressive feeling on the occupant through the webbing, which results in a feeling of fatigue given to the occupant after a long period of driving and a decreased utilization rate of the seatbelt system.
There has been proposed a seatbelt wind-up device capable of giving comfortable driving to the occupant by exerting no wind-up biasing force on the occupant after the webbing is fastened to the occupant. Said seatbelt wind-up device is constructed such that a pawl is brought into mesh with a ratchet wheel fixed on a webbing-winding drum to prevent the wind-up and wind-off rotations of the winding drum, a solenoid to be actuated by a collision sensing switch and seatback switch is connected to said pawl, and the pawl is separated from the ratchet wheel to allow the winding drum to rotate when necessary.
More particularly, the normal driving posture of the occupant is detected by the seatback switch incorporated in the occupant's seat, and in this normal driving posture, the solenoid is made inoperative, whereby the pawl is engaged with the ratchet wheel to stop the rotation of the winding drum, thus preventing the biasing force from being exerted on the webbing. While, in an emergency of the vehicle, a collision sensing switch makes the solenoid inoperative, whereby the pawl is brought into meash with the ratchet wheel by the biasing force, thus preventing the rotation of the winding drum.
However, in the seatbelt system of the type described, the switch provided on the seatback of the occupant's seat is adapted to detect the normal driving posture of the occupant; hence, the wiring from said switch to the seatbelt wind-up device is very complicated and moreover, it is impossible to reliably detect the normal driving posture of the occupant. Namely, the occupant is not always pressing the upper half of his body against the seatback in the normal driving posture, in which case, the seatback switch is not closed, whereby the wind-up biasing force is still exerted on the occupant as the uncomfortable oppressive feeling.